If you attach a device like a light bulb or intercooler water spray pump to a variable voltage power supply, you’ll soon see that boosting the voltage changes how the item behaves. Lift the voltage and fans blow harder, pumps push better and lights glow more brightly. So if you can boost the voltage going to the device, it will in many cases work better.
But until recently, voltage boosters were expensive and hard to get. However, now all that has changed. Through eBay and via China, you can now get an electronic module that will boost normal car voltages to 15, 16, 18 or even 24V, all with just the movement of a switch! And best of all, at the time of writing, these boosters are available for a total cost of AUD$17 – including postage!
So how do you use this device – and what are the good and bad points of taking this approach?
The Voltage Booster
The voltage booster is sold as a car power supply for laptops. Because many laptops need more than 12V DC to run, unless the voltage is boosted, you can’t run such a laptop from a car power supply. The universal adaptor has a power rating of 80 watts (more on this in a moment!), plugs into the cigarette lighter and has eight interchangeable plug tips to suit different laptop power sockets. It is switchable for 15, 16, 18, 19, 20, 22 and 24V outputs. It is also overload protected.
The same item is available from lots of different eBay sellers – have a good look around for the combination of lowest purchased price + shipping cost, along with good seller feedback. Mine arrived in less than a week.
The most important limitation to realise is that while the device is nominally rated at 80 watts, we found that in the real world, this figure should be halved to 40 watts. That is, you can’t run the voltage booster with a 50W headlight in order to brighten your main beam.
Another way of expressing that wattage is to say that the standard current draw of the device shouldn’t be more than about 3 amps. In turn, that excludes high current fuel pumps that can easily draw up to 10 amps, and radiator fans that can take up 20 amps.
So what can you run?
You can use the Voltage Booster to easily increase the pressure and output of windscreen washer pumps commonly used for intercooler water sprays.
You can use it to boost the output of interior lights, brake lights and reversing lights. Depending on the measured current draw, you can also use it to boost the flow of water/air intercooler water pumps.
In non-automotive applications, you can use it to maintain the output of a nominally 12V lighting system, even as battery voltage falls.
In testing, we found that the system would provide its boosted output down to an input voltage of just 8.5V. To put that another way, there would be no change in light brightness from a fully-charged battery of 13.8V to a dead flat battery at 8.5V!
So the voltage booster would be ideal with a miniature 20W halogen being run off a 12V SLA battery – a great, cheap, cycle lighting system.
Finally, where low current 24V devices need to be run off 12V, this adaptor is ideal. Examples include using truck instrumentation (eg turbo exhaust gas pyrometers) in cars.
We ran the voltage booster at near full load and assessed what happened. In short, it got hot. The internal heatsink was much too hot to touch, as were some of the PCB tracks. However, if you really wanted a high power rating, you could:
Replace the heatsink (arrowed) with a larger one
Run solder over the wide, hatched PCB tracks (so increasing their current carrying capacity)
Increase the wire thickness used in the input lead
Add a small 12V fan
But what happens to the device you’re powering when you increase the voltage going to it?
In short, not only will its performance improve, but its life will be reduced. In many cases, that’s of little concern – something like an intercooler water spray pump is used so little (in relative terms) that its life will still be fine. Incandescent light bulbs will have a shorter life, but as they’re a replacement item, again it’s no big deal.
However, you should select the increase in voltage with care. A motor (eg a pump) used infrequently in short bursts could be run at 18V without many issues, but a lamp being used for long periods shouldn’t be fed much over 15V. In general, make sure that items don’t get too hot!
Note that devices that use internal voltage regulators, or are current limited, shouldn’t be run at higher than normal voltages. Normally, there will simply be no difference in the performance of the device but in some cases (eg LEDs using dropping resistors), the device may be damaged by over-current. So LEDs and electronic bits and pieces like car radios and other electronic modules aren’t suitable for running at higher voltages.
Using the voltage booster is dead simple. Cut off the input cigarette lighter plug and the output multipurpose plug. (Make sure before you do this that you mark the input and output cables!).
In each case, the braided part of the cable is the ground (earth) connection, and the white lead the positive. The input to the voltage booster is wired to the fused supply, and the output to the device you’re powering, in the case of pumps and fans, making sure you use the correct output polarity. And that’s it!
The real beauty of the device is that you can boost output without having to change what it is that you’re powering. So the original washer pump can stay in place – just alter the power feed to it. If you’re up-rating bulbs, you don’t need to find new higher wattage bulbs of the same fitting – just bump-up the voltage going to them.
Cheap, simple and effective!